(a) Field of the Invention
The present invention concerns, as a new industrial product, a composite article particularly useful for making waterproof and thermally insulated prefabricated coverings, in the civil and industrial building art. The new product is particularly useful for making curved roofs and/or slabs, slanted at a grade of more than 5%.
(b) Prior Art
As is known, a significant portion of the waterproof coverings in civil and industrial building is made by using discontinuous elements such as e.g. fibro-cement sheets, metal and plastic sheets, and tiles of various types.
The fibro-cement sheets, commonly known by the name of "Eternit" trademark of Eternit S.p.A. of Genova, Italy, are constituted by a mixture of cement and asbestos and are laid on an cement support and are usually connected by mechanical joints whereby they create a type of covering which is widely used specially in industrial buildings.
Another type of very common, discontinuous elements covering is constituted by associated tiles, either of a traditional type (hollow tiles) or concrete tiles, or natural tiles (slate tiles) or bituminous tiles (these latter better known as "asphalt shingles"). These latter are constituted by a felt-cardboard or a glass mat inpregnated with bituminous substances, are covered on their surfaces with granulated materials having various colours and are available in a great variety of shapes.
The tiles are normally applied on a wood or concrete support and the waterproof covering is built up by superimposing one element on the other. In some cases the elements of the covering are fixed to their support by mechanical means.
The prior art covering elements hereinbefore described have certain drawbacks.
In particular, the fibro-cement sheets, besides being intrinsically fragile due to the type of material employed, meet with ever increasing obstacles to their use because of the presence of asbestos in their composition. Certain countries have even forbidden the use of asbestos.
Further it may be necessary to use, with this type of discontinuous elements covering, gaskets and seals to reach the desired degree of air fastness.
A significant factor which limits the use of the prior art covering elements of the type hereinbefore specified is their weight which may attain in certain cases, e.g. in the case of cement tiles, rather high values (70-75 kg/m.sup.2). This, of course, causes an increase in costs because the support has to be designed in such a way as to bear high loads.
Further, a covering may be made from tiles only if the design contemplates a slant of the roof of at least 20%: otherwise water may always infiltrate through the abutments of the various discontinuous elements which constitute the covering. Even when the covering has been designed with the appropriate slant, there is always the danger of water infiltrations due to particular atmospheric phenomena. Certain conditions of wind strength and direction may in fact force the water through the abutments between different covering elements.
It is also known that all new buildings must be thermally insulated due to the ever increasing cost of energy; specific laws and decrees which have been enacted in many countries in the last years prescribe the limiting values of the heat transmission coefficient K which are permissible in new buildings.
The thermal insulation of a covering made from discontinuous elements may be a costly operation from the installation viewpoint inasmuch as, as a general rule, a vapour barrier layer must firstly be provided, and it must be followed by the application of insulating means and finally by the installation thereabove of the discontinuous elements which constitute the covering.
The insulating materials presently used have to be applied by using adhesives of various nature, in the hot, in the cold, glues, adhesive ribbons, mechanical fixing means, welding, etc. This obviously complicates the operation of applying the insulating means by introducing a supplementary work phase and further creates various problems related in each instance to the specific nature of the adhesive means employed.